clippy_lints/src/redundant_field_names.rs

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::meets_msrv;
   3 use rustc_ast::ast::{Expr, ExprKind};
   4 use rustc_errors::Applicability;
   5 use rustc_lint::{EarlyContext, EarlyLintPass};
   6 use rustc_middle::lint::in_external_macro;
   7 use rustc_semver::RustcVersion;
   8 use rustc_session::{declare_tool_lint, impl_lint_pass};
   9
  10 const REDUNDANT_FIELD_NAMES_MSRV: RustcVersion = RustcVersion::new(1, 17, 0);
  11
  12 declare_clippy_lint! {
  13     /// **What it does:** Checks for fields in struct literals where shorthands
  14     /// could be used.
  15     ///
  16     /// **Why is this bad?** If the field and variable names are the same,
  17     /// the field name is redundant.
  18     ///
  19     /// **Known problems:** None.
  20     ///
  21     /// **Example:**
  22     /// ```rust
  23     /// let bar: u8 = 123;
  24     ///
  25     /// struct Foo {
  26     ///     bar: u8,
  27     /// }
  28     ///
  29     /// let foo = Foo { bar: bar };
  30     /// ```
  31     /// the last line can be simplified to
  32     /// ```ignore
  33     /// let foo = Foo { bar };
  34     /// ```
  35     pub REDUNDANT_FIELD_NAMES,
  36     style,
  37     "checks for fields in struct literals where shorthands could be used"
  38 }
  39
  40 pub struct RedundantFieldNames {
  41     msrv: Option<RustcVersion>,
  42 }
  43
  44 impl RedundantFieldNames {
  45     #[must_use]
  46     pub fn new(msrv: Option<RustcVersion>) -> Self {
  47         Self { msrv }
  48     }
  49 }
  50
  51 impl_lint_pass!(RedundantFieldNames => [REDUNDANT_FIELD_NAMES]);
  52
  53 impl EarlyLintPass for RedundantFieldNames {
  54     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
  55         if !meets_msrv(self.msrv.as_ref(), &REDUNDANT_FIELD_NAMES_MSRV) {
  56             return;
  57         }
  58
  59         if in_external_macro(cx.sess, expr.span) {
  60             return;
  61         }
  62         if let ExprKind::Struct(ref se) = expr.kind {
  63             for field in &se.fields {
  64                 if field.is_shorthand {
  65                     continue;
  66                 }
  67                 if let ExprKind::Path(None, path) = &field.expr.kind {
  68                     if path.segments.len() == 1
  69                         && path.segments[0].ident == field.ident
  70                         && path.segments[0].args.is_none()
  71                     {
  72                         span_lint_and_sugg(
  73                             cx,
  74                             REDUNDANT_FIELD_NAMES,
  75                             field.span,
  76                             "redundant field names in struct initialization",
  77                             "replace it with",
  78                             field.ident.to_string(),
  79                             Applicability::MachineApplicable,
  80                         );
  81                     }
  82                 }
  83             }
  84         }
  85     }
  86     extract_msrv_attr!(EarlyContext);
  87 }